Embodiments of the present disclosure relate to a prism sheet, a backlight module and a liquid crystal display device thereof.
As a kind of flat panel displays, liquid crystal displays (LCDs) comprise liquid crystal which does not emit light by itself, but are provided with backlights to emit light. For example, a backlight module comprises: a molded frame for fixing; a reflective sheet mounted on a lowermost surface for reflecting light to a liquid crystal panel; a light guide plate provided on the reflective sheet for guiding light; a light source provided between the light guide plate and a side wall of the frame for emitting light; a diffusion sheet provided on the light guide plate for making illumination uniform; a prism sheet provided on the diffusion sheet for converging light; a protective sheet for protecting the diffusion sheet and the prism sheet; and other optical film sheets.
Typically, a prism sheet used in a backlight module of a LCD has a triangular cross-section. In order to achieve an effect of light concentration in both horizontal and vertical directions, commonly two prism sheets are provided, with one prism sheet being in the X-direction and the other prism sheet being in the Y-direction respectively. With the two prism sheets, not only the thickness of the backlight module and the number of parts are increased, but also the two prism sheet are more likely to scratch each other; moreover, a limited view angle is caused by the triangular design.
Recently, a kind of a prism sheet, that is, a reverse prism is provided in the related art, which cooperates with a light guide plate having a prism structure. The prism structure on the light guide plate engages with the reverse prism sheet disposed thereon, which can mitigate the mutual scratch degree. However, the contact surfaces for engagement are very small. As a result, it is very possible to run into an unstable engagement.